A variety of increasingly sophisticated mechanisms and control systems are now being used in manufacturing, processing, and handling industries to automatically control parts-handling and forming machines. Many of these machines utilize complicated mechanisms to feed and process materials. Furthermore, there exist many different mechanisms to feed, sort, convey, manipulate, and/or form materials. In some cases, all these features are provided in a single machine capable of fast and efficient operation. Such sorting, feeding, work handling and processing mechanisms typically utilize drive control systems to articulate complex kinematic linkages in order to move working elements of the machine to desired positions. A drive control system includes an electric motor, such as an AC servomotor, and a servo drive motor controller. However, for the case of a multiple mechanism machine it becomes necessary to choreograph operation of each drive and element. Such a combination of mechanisms provides a multiple drive/multiple output machine suitable for a number of cycle based processes. Typically, a control system directs operation of the drive controls to impart desirable cooperative motions to all of the linkages. In this manner, a part can be manipulated through a series of operating steps.
One way of imparting desirable kinematic properties to a multiple drive/multiple output machine is to design each mechanism with combinations of kinematic linkages that have well-understood properties. Ratchets, cams, gears, chain and sprocket drives, linkages, toggles, and various coupling devices are typically used to create a linkage that produces a desired displacement-based movement of a part or element. For example, a Watts linkage is one device utilized to produce a substantially straight line motion of an element in a machine. Various other exemplary linkages are known for producing straight-line, or nearly straight-line motion. Additionally, other similar linkage designs are known for producing desired arcuate, circular, and rotary motions of a machine element. However, a machine having single dedicated motion cannot be easily modified in order to suit a particular desired machine application.
Another way of imparting desirable kinematic properties to a multiple drive/multiple output machine is to utilize robotic arms to form each moving mechanism. Such arms are capable of manipulating an element or part according to nearly any desired path of motion. Additionally, the robotic arms can usually be easily reprogrammed. Typically, a computerized control system directs operation of the robotic arm, enabling production of such a desired path-wise motion. Such robotic machines are choreographed according to a desired path-wise, or position-based motion of each mechanism. In this manner, clearance between elements during an operation can be ensured. Furthermore, desired positioning of a part being operated on can be ensured, in relation to a machine element doing the operating. However, robotic arms are not well suited for machines using repetitive cycle-based processes.
One problem encountered with utilizing kinematic linkages to position a working element is the inability to vary the positioning of the element or part over time and distance without redesigning the linkage. Redesign of the linkages typically takes a significant amount of machine setup time. For example, a cam on a cam follower mechanism must typically be changed in order to vary kinematic characteristics of a particular machine element using the cam follower mechanism. The only possible variation available is to speed up or slow down operation of the cam, which complicates control of the device. However, movement is still directly related to the shape of the cam, which remains the same. Therefore, there is a need to better control kinematics of machine elements in a way that allows for relative changes in velocity of the element or part over time. Furthermore, there is a need to control elements of a machine based on the velocities of each element in order to produce smooth contacts between parts, and smooth transitions between processing steps being performed by a machine.
Another problem encountered with utilizing kinematic linkages to position a working element is the complexity needed to produce a desired motion, especially when it is necessary to vary velocity of the element. For example, an indexing mechanism can be formed from an epicyclic gear and a cam. In such a construction, a planetary wheel and a cam are fixed relative to one another. A carrier is rotated around the fixed wheel at a uniform speed. An index arm is supported at one point along the carrier, and at another point along the follower. The arm moves relative to the cam, along the follower to produce a non-uniform motion of the arm, having dwell periods. However, such a linkage proves rather complicated for producing a specific non-uniform rotary motion of the arm.
A further problem is encountered when utilizing robotic arms to position a working element of a multiple drive/multiple output machine because a complex control scheme is needed to choreograph timing and motions of each robotic arm. Typically, motion studies must be made with mocked-up machines in order to ensure desired placement of each robot arm with respect to the other arms of the machine.
Yet another problem with utilizing robotic arms on a machine results from the relatively high cost of configuring a multiple drive/multiple output machine. A typical robotic arm has up to six degrees of freedom, with as many as six independently operable solenoid motors configured to articulate the arm to desired positions. Target positions are used to choreograph the positioning of each arm over time. However, it is difficult, if not impossible, to configure motion of each robotic arm with respect to the other arms based on velocity of the end element on each arm. A velocity controlled motion would enable smoother contact and/or cooperation between machine elements. Therefore, there is a need to configure machine element motion between mechanisms based upon velocities of each working element of the machine.